This invention relates to blends of polyarylene ether resins and monovinylidene aromatic polymers such as polystyrene.
Polyarylene ether resins are well-known articles of commerce. These polymeric materials are thermoplastic engineering resins available in a variety of molding and extrusion grades. They combine high heat, flame retardancy and high impact properties with one of the lowest moisture absorption rates in engineering resins. The polyarylene ether resins are known for their (1) excellent mechanical properties, such as tensile strength, (2) electrical properties such as volume inherent resistivity and dielectric strength, and (3) high heat distortion temperature. However, they are difficult to process because of their high melt viscosity and high softening point, coupled with a low resistance to oxidation with heat.
Improvements in processability of polyarylene ether compositions have been obtained by blending with other resins, but usually at the expense of other properties. Polystyrene has been the most widely used blend material, because the polystyrene and the polyarylene ether, unlike most mixtures of polymeric materials, are substantially completely compatible to the extent that blends of these two polymers form true alloys and retain much of their base resin properties. For example, the blends have a single glass transition temperature T.sub.g, which is the temperature at which an amorphous material such as glass or high polymer changes from a brittle, vitrious state to a plastic state. The tensile strength, heat deflection temperature, melt viscosity and other physical properties of the polyarylene ether-polymonovinylidene aromatics are a weighted average of the values corresponding to the individual components.
In addition to the use of polystyrene as a modifier for polyarylene ether resins, polyamides (U.S. Pat. No. 3,379,792), polyolefins (U.S. Pat. No. 3,351,851), rubber-modified styrene resins (U.S. Pat. Nos. 3,383,435 and 3,959,211 and Ger. Offen. No. 2,047,613), and mixtures of polystyrene and polycarbonate (U.S. Pat. Nos. 3,933,941 and 4,446,278) have been proposed as suitable modifiers for polyarylene ether resins.